Spam, Spam, Spam, Spam......

Written by Phil Taylor on Saturday, 13 November 2010. Posted in Technical Articles

What can you do about spam?

Few people can use Internet email today without experiencing the phenomenon now known as spam. I am not talking about the SPiced hAM product originally produced by George Hormel in 1937. I am talking about unsolicited commercial email (UCE) which is a practice of sending 'bulk' emails generally advertising a product or service.

Monty Pythons Vikings
How did this ever end up getting called spam? I hear you ask. Many of you will remember the Month Python sketch when a group of Vikings sang "spam, spam, spam, spam" in an increasing crescendo, thus drowning out all other conversation. Hence, the analogy applied because UCE effectively drowns out normal discourse on the Internet.

How do I deal with SPAM?
How many times have you opened your inbox to find it full of pornography, pyramid selling schemes and other such rubbish? This can not only be annoying and sometimes offensive, but, when there is so much rubbish it can often be difficult to sort the "wheat from the chaff" and you can risk losing important emails.

There are various 'spam blockers' available but unfortunately none of them are ever 100% effective. Primarily because spammers (people that send spam) invest almost as much time into coming up with ways of fooling spam blockers as we invest in blocking them. As a general rule of thumb though, you can expect at least 80-90% effectiveness, which, while not perfect does make it much easier to see which emails are valid.

One difficulty with spam-blockers is the possibility of 'false positives', this is when the blocking software believes an email is spam when it isn't. These can often be caused by lengthy disclaimers at the bottom of messages containing various legal words and phrases which trigger the keyword checking option within the spam-blocker. Unfortunately, the only thing to do in this situation is to relax the keyword checking rules or to periodically check through the suspected spam that you have received.

While there are now a myriad of commercial and free spam-blockers available, they fall basically into two categories, client side and server side. A client-side spam-blocker runs in conjunction with your email program (Outlook/Outlook Express, Eudora etc) and checks any email that you have downloaded from your ISP (Internet Service Provider) and performs various checks before either moving the messages to a separate folder, prefixing the subject with (for example) the word spam or (not recommended) deleting it. The main problem with this type of program is that the message must be fully downloaded before the software can determine whether it is spam or not so if you use a dial-up connection, this will not help your 'phone bill.

Server-side spam-blockers tend to be installed on a companies mail server and can perform various checks before the email is even accepted for delivery. One of the most effective of these checks is called an RBL lookup (Realtime Blackhole List). There are various RBL's some commercial and some run by people opposed to the practice of sending spam. They allow your mail server to check (in real time) the unique IP address that the email is being sent from against a list of known spammer or spammer friendly addresses and if a match is found your mail server can deny the connection.

The Reverend Thomas Bayes
Another feature often found in both client and server based spam-blocking software is Bayesian analysis. Bayesian analysis is formulae developed by statistician Reverend Thomas Bayes as a means of calculating, from the number of times an event has not occurred, the probability that it will occur in the future. This though had nothing to do with email as he died in 1761 but in practice, by providing a sample of known good emails together with known bad (spam) emails, a Bayesian filter can quite accurately block spam and if provided with enough data can help to reduce false positives down to a more than manageable level.

If you feel that you have a problem with SPAM in your business, or that SPAM is hindering you in your day to day work, please contact your shine Systems account manager who will be pleased to discuss with you what options are available to you to reduce this problem. shine Systems can offer a number of different products to meet your specific requirements.

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About the Author

Phil Taylor

Phil Taylor is the Technical Director of shine Systems. Since completing an Electronic Apprenticeship at Racal in 1991, Phil has specialised in the design and installation of all types of networked computer systems.

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